If it is just a clone trying to copy the same idea it usually does not work so well, but if you have a good and different idea that can be based on the same platform why not focus on it and end up with a successful product. The problem is that most of these are simply going to be clones and being simply a clone of something successful and established is never a good idea, even if you are based off the same source code.
Here is an example - the Brave browser, it is based off Chromium, so they are not trying to reinvent the core browser from the ground up, but are focusing on some features that are what users want - privacy, safety and of course getting rewarded for the thing that you are already doing every day - browsing the Internet. So far the project seems promising, but we are yet to see if it will end up successful and be able to deliver on the promisses they make.